1. Field of the Invention
This invention relates to an articulated tube structure for use in fiberoptic endoscopes or like instruments. More specifically, the invention pertains to an articulated, four-way bendable tube structure which may be arranged between the head and flexible tube of an endoscope or the like for permitting the endoscope head to be tilted, by selective manipulation of pull wires extending through the articulated tube structure and flexible tube, in either of four different directions at angular spacings of 90.degree.. Such four-way bendable tube structures are in constrast to two-way bendable ones which can be bent in only two opposite directions.
2. Description of the Prior Art
An articulated, four-way bendable tube structure of the kind under consideration usually comprises a series of relatively short tubular sections jointed end-to-end so as to be bent in four different directions via four corresponding pull wires passed therethrough. In the use of the tube structure in an endoscope, the pull wires are affixed each at one end to the head of the endoscope at its distal end, which is to be inserted into a desired body cavity or the like to be visualized, and are intended to be pulled selectively at the proximal end of the endoscope.
For supporting such pull wires in position within the articulated tube structure, it has been suggested and practiced to form longitudinal channels in the internal surfaces of its constituent sections as by means of a press. Alternatively, an inner tubular member has been employed which has longitudinal depressions or channels formed in its external surface, also by a press, and which is fitted in each constituent section of the tube structure, with the pull wires accommodated in the respective channels. These prior art means are unsatisfactory because the pull wires are required to make extensive sliding contact with the tube sections, with or without the inner members, and also because the pressing operation performed on the tube sections, usually made of stainless steel or the like, may result in the production of rugged edges.
Another objection to the conventional articulated tube structure concerns the unevenness of its internal surfaces. Such unevenness arises from the fact that, in interconnecting the constituent sections of the tube structure, lugs or other projections on one end of each section are displaced inwardly so as to underlie projections on the opposed end of the adjacent section. The uneven internal surfaces of the tube structure is undesirable as it is intended to accommodate a flexible bundle of light transmitting optical fibers, in addition to the pull wires.